fix: Fix medium width layout

- col-md-3
- col-md-2
- col-md-7

The sum should be 12 (3+2+7).

Author: toshimaru

Diff for: src/_layouts/default.html

@@ -55,11 +55,11 @@
         </div>
       </nav>
 
-      <div class="col-12 col-md-3 col-xl-2 toc-content-sticky">
+      <div class="col-12 col-md-2 col-xl-2 toc-content-sticky">
         <div class="toc-content">{% toc %}</div>
       </div>
 
-      <main role="main" class="col-12 col-md-9 col-xl-8 py-md-3 pl-md-4">
+      <main role="main" class="col-12 col-md-7 col-xl-8 py-md-3 pl-md-4">
         {{ content }}
         <footer class="site-footer">
           <!-- <span class="site-footer-credits">This page was generated by <a href="https://pages.github.com">GitHub Pages</a>.</span> -->